Save $30, invest $10 in sports gambling. With the right knowledge and research, you can increase that $10 to $300 in a month... ofcourse there's always a probability that you lose all the $10.
If I have to invest my money, I'll make sure that I am investing in a business that will give me a ROI. investing in gambling is risky, there is nothing sure in it. $40 a day is big enough and if it is from OP's job, I think OP should just save it or engage in business by himself and not to invest it to any one who offers him something. It is safer that way, only that it will require attention.